A packet switched communication system like the internet comprises interconnected nodes for the forwarding of data packets. Edge nodes connect the communication system to user equipment or further communication systems. Presently data packets in the internet are processed according to best effort service, i.e. all data packets are processed with equal priority.
In order to provide a defined quality of service for the internet which supplements the best effort service, the differentiated services model was introduced (IETF RFC 2474 and 2475). In the differentiated services model, a data field in the data packets specifies the handling at the nodes which forward them. The packet header according to the internet protocol (IP) of both IP version 4 and IP version 6 comprises a data field which is denoted as differentiated services (DS) field and has a length of 8 bits. The nodes perform a differentiated handling of the packets according to the first 6 bits of the DS field which specify the per hop behavior while the last two bits are presently not used. Correspondingly, it has been proposed that the definition of the DS field in the IP protocol should only comprise the bits specifying the per hop behavior instead of the entire DS field.
According to the value of the per hop behavior, a decision is performed in the node whether, in which way and with which priority packets are queued or if the packets can be dropped in case of congestion in the node. The default handling is the present best effort service. Other per hop behaviors which have been proposed represent for example expedited forwarding (EF) of the packets or assured forwarding (AF).
In communication systems like GSM (global system for mobile communications) or subscriptions which correspond to different traffic precedences (European Standard ETSI EN 301 344 V 6.4.0; 3rd Generation Partnership Project, Technical Specification 3G TS 23.060 V 3.1.0). Subscription information specifying the resources which are to be allocated for forwarding traffic of the user are stored in a data base in the system. Generally, a record is kept in a data base denoted as the home location register (HLR) serving the user, in many systems with a copy in a visitor register (VLR) serving the area in which the user is presently located. If a connection is set up for the user, a data base is contacted which resources, for example bandwidth, are to be allocated to the user for the connection to the core network, e.g. on the radio link. It is possible that a negotiation process with the user equipment is performed during the access and the allocated resources differ from the record entry by taking into account the available resources under the present traffic conditions.
In the core network which interconnects the nodes for the access of the communication system, data and control signaling is often forwarded as packet switched traffic. As an example, in the GPRS (general packet radio service) and UMTS core network, the internet protocol is used for routing traffic on the routing layer evaluated by the nodes forwarding the packets. Correspondingly, connections are often packet switched sessions wherein the packets of a connection can be routed over different links and the traffic on a connection is not necessarily continuous.
If the traffic load in the core network is high, the forwarding of the data packets bearing the traffic through the core network is of increasing importance. No method is presently available in the core network to distinguish between different user subscriptions. It is only possible to specify a traffic priority which can be set by any user according to his wishes and which does, therefore, depend highly on the behavior of other users. Consequently, the traffic of users is forwarded in the core network without predictable priority and messages can be delayed in case of congestion. Especially delay sensitive applications can be impaired, even if the resources allocated to the user in the access network are sufficient for the connection.